All models participating
in the Intergovernmental Panel on Climate Change
Fourth Assessment Report (IPCC AR4) show declining Arctic ice cover
over
this period. However, depending on the time
window for analysis, none or very few individual model simulations show
trends
comparable to observations.

These images compare ice age, a proxy for ice thickness, in 2007, 2008, 2009, and the 1981–2000 average. 2009 saw an increase in second-year ice over 2008. At the end of summer 2009, 32% of the ice cover was second-year ice and three-year and older ice were 19% of the total ice cover, the lowest in the satellite record.

Note: The maps show the area of the Greenland ice sheet with at least one day of surface melting in summer. The diagram shows the cumulated melt area, which is defined as the annual total sum of every daily ice sheet melt area. For example, if a particular area is melting on 20 days in a given year, it is counted 20 times.